– Associate Professor - HLA Laboratory Director, Baylor College of Medicine, United States
Body: Patient: 6 year-old male, blood type A, had a previous kidney transplant two years ago and was up for his second renal transplant. The virtual XM assessment was negative with no DSA and no antibodies found against the previous donor. Based on this information the patient was transplanted. During surgery the patient needed a blood transfusion. After 10 days a biopsy presented strong AMR with C4d deposition and hemorrhage. As urine output was decreased, increasing levels of Thymoglobulin were given. The level of lymphocyte counts remained unchanged. Serum at 10 days was checked for DSA and there was a significant de-novo anti-HLA and an anti-Bw4 pattern. These DSA significantly increased post nephrectomy with B57 over 22K MFI and DQ7 18K MFI. We tested a segment from the transfused unit, and it was void of HLA Ab. We thought this could have been due to a memory response previously or the current transfusion’s platelets. We explored further into non-HLA Ab testing on this patient pre and post txp. We found a very significant AT1R Ab titer >40 U/mL pre txp and 23 U/mL 10 days post txp and tapered to 17 U/mL borderline. On our non-HLA Ab panel of 60 antigens, Human Transferrin and GAPDH were detected pre txp and after 10 days post Human Transferrin decreased, yet SSB increased to 6309 MFI. The patient did have a positive auto FXM for T cells (263 MCF) and small shift for B cells (24 MCF). The positive auto XM made it challenging to interpret the allo FXM as the T cell (113 MCF) and B cells (127 MCF) were borderline with our positive T/B cells cutoffs at 75 and 100 respectively. Lastly, the patient received Thymoglobulin in his first transplant. The patient developed significant heterologous antibodies against rabbit when Thymoglobulin was given that limited its effectiveness. This would explain why Thymoglobulin was not effectively dropping the patient’s lymphocyte count.
Conclusion: This case illustrates the various antibodies that can be detrimental to the kidney graft leading to acute AMR and graft loss. The patient’s memory response was strong, and re-transplantation will be a challenge. Selecting a future kidney donor will include avoiding Bw4 and DQ7 antigens, switching Thymoglobulin to Atgam, an Equine alternative, and treat the patient with Losartan, an AT1R blocker. These steps may provide a window for a third long lasting kidney transplant off dialysis.
